1. Resource Acquisition and Transport CO2 O2
Light
H2O
Sugar
Figure 36.2 An overview of resource acquisition and transport in a vascular plant O2
H2O and minerals
CO2

2. Leaf area index Ground area covered by plant
Figure 36.4 Leaf area index
Plant A Leaf area = 40% of ground area (leaf area index = 0.4)
Plant B Leaf area = 80% of ground area (leaf area index = 0.8)

3. mycorrhiza, a symbiotic association of fungi and roots
2.5 mm
Figure 36.5 A mycorrhiza, a symbiotic association of fungi and roots

4. Proton pumps provide energy for solute transport
CYTOPLASM
EXTRACELLULAR FLUID _ + _ + H+
Proton pump generates mem- brane potential and gradient.
ATP _ H+ + H+ H+ H+ H+ _ H+ + H+
Figure 36.6 Proton pumps provide energy for solute transport _ H+ +

5. Solute transport in plant cells_
CYTOPLASM +
EXTRACELLULAR FLUID _ + K+ _ K+ + K+ K+ K+ _ K+ K+ + _
Transport protein +
(a) Membrane potential and cation uptake _ + H+ H+
NO3−
NO3− _ + _ + H+ H+ H+ H+ H+ H+
NO3−
NO3− _ +
NO3− _
NO3− + H+ H+ _ H+ + H+
(b) Cotransport of an anion with H+
Figure 36.7 Solute transport in plant cells _ + S H+ H+ _ H+ H+ + _ H+ + H+ S H+ H+ H+ H+ S S _ + S H+ _ + H+ _ S H+ +
(c) Cotransport of a neutral solute with H+

6. Cotransport - a transport protein couples the diffusion of one solute to the active transport of another. _ + H+ H+
NO3− _
NO3− + _ + H+ H+ H+ H+ H+ H+
NO3− _
NO3− +
NO3− _
NO3− + H+ H+
Figure 36.7b Solute transport in plant cells _ H+ + H+
Cotransport of an anion with H+

7. Water potential and water movement.
(b)
(c)
(d)
Positive pressure
Increased positive pressure
0.1 M solution
Negative pressure (tension)
Pure water
H2O
H2O
H2O
H2O
ψP = 0 ψS = 0
ψP = 0 ψS = −0.23
ψP = 0 ψS = 0
ψP = ψS = −0.23
ψP = 0 ψS = 0
ψP = ψS = −0.23
ψP = −0.30 ψS = 0
ψP = 0 ψS = −0.23
Figure 36.8 Water potential and water movement: an artificial model
ψ = 0 MPa ψ
= −0.23 MPa
ψ = 0 MPa
ψ = 0 MPa
ψ = 0 MPa
ψ = MPa
ψ = −0.30 MPa
ψ = −0.23 MPa

8. Water relations in plant cells
Initial flaccid cell:
ψP = 0 ψS = −0.7
0.4 M sucrose solution:
ψ = −0.7 MPa
Pure water:
ψP = 0 ψS = −0.9
ψP = 0 ψS = 0
ψ = −0.9 MPa
ψ = 0 MPa
Plasmolyzed cell
Turgid cell
ψP = 0 ψS = −0.9
ψP = 0 ψS = −0.7
ψ = −0.9 MPa
ψ = 0 MPa
Figure 36.9 Water relations in plant cells
(a) Initial conditions: cellular ψ > environmental ψ
(b) Initial conditions: cellular ψ < environmental ψ

9. Cells in wilted plant to the left - plasmolysis
A wilted Impatiens plant regains its turgor when watered
Cells in wilted plant to the left - plasmolysis
Cells in plant below - turgor.
Figure A wilted Impatiens plant regains its turgor when watered

10. Short Distance Transport
Cell wall
Cytosol
Vacuole
Plasmodesma
Vacuolar membrane
Plasma membrane
(a) Cell compartments
Key
Apoplast
Apoplast
Transmembrane route
Apoplast
Symplast
Figure 36.11a Cell compartments and routes for short-distance transport
Symplast
Symplastic route
Apoplastic route
(b) Transport routes between cells

11. Transport of water and minerals from root hairs to the xylem
Casparian strip
Endodermal cell
Pathway along apoplast
Pathway through symplast
Casparian strip
Plasma membrane
Apoplastic route
Figure Transport of water and minerals from root hairs to the xylem
Vessels (xylem)
Symplastic route
Root hair
Epidermis
Endodermis
Stele (vascular cylinder)
Cortex

12. Transport of water and minerals from root hairs to the xylem
Casparian strip
Plasma membrane
Apoplastic route
Vessels (xylem)
Figure Transport of water and minerals from root hairs to the xylem
Symplastic route
Root hair
Epidermis
Endodermis
Stele (vascular cylinder)
Cortex

13. Pathway along apoplast
Casparian strip
Endodermal cell
Pathway along apoplast
Pathway through symplast
Figure Transport of water and minerals from root hairs to the xylem

14. Guttation
Figure Guttation

15. Generation of transpiration pull
Cuticle
Xylem
Upper epidermis
Microfibrils in cell wall of mesophyll cell
Mesophyll
Air space
Figure Generation of transpirational pull
Lower epidermis
Cuticle
Stoma
Microfibril (cross section)
Water film
Air-water interface

16. Ascent of xylem sap Figure 36.15 Ascent of xylem sap Xylem sap
Outside air ψ = −100.0 Mpa
Mesophyll cells
Stoma
Stoma
Leaf ψ (air spaces) = −7.0 Mpa
Water molecule
Transpiration
Leaf ψ (cell walls) = −1.0 Mpa
Atmosphere
Adhesion by hydrogen bonding
Xylem cells
Cell wall
Water potential gradient
Trunk xylem ψ = −0.8 Mpa
Cohesion by hydrogen bonding
Cohesion and adhesion in the xylem
Figure Ascent of xylem sap
Water molecule
Root hair
Trunk xylem ψ = −0.6 Mpa
Soil particle
Soil ψ = −0.3 Mpa
Water
Water uptake from soil

17. Water molecule Root hair Water Water uptake from soil Soil particle
Figure Ascent of xylem sap
Water
Water uptake from soil

18. Adhesion by hydrogen bonding
Xylem cells
Cell wall
Figure Ascent of xylem sap
Cohesion by hydrogen bonding
Cohesion and adhesion in the xylem

19. Xylem sap Mesophyll cells Stoma Water molecule Transpiration
Figure Ascent of xylem sap
Transpiration
Atmosphere

20. An open stoma (left) and closed stoma (right)
Figure An open stoma (left) and closed stoma (LMs)

21. Stomatal Openings
Guard cells turgid/Stoma open Guard cells flaccid/Stoma closed
Radially oriented cellulose microfibrils
Cell wall
Vacuole
Guard cell
(a) Changes in guard cell shape and stomatal opening and closing
Guard cells turgid/Stoma open Guard cells flaccid/Stoma closed
H2O
H2O
H2O
H2O
Figure Mechanisms of stomatal opening and closing
H2O K+
H2O
H2O
H2O
H2O
H2O
(b) Role of potassium ions in stomatal opening and closing

22. Xerophytic - Desert Plants Adaptations
Ocotillo - leafless
Xerophytic - Desert Plants Adaptations
Oleander leaf cross section and flowers
Cuticle
Upper epidermal tissue
100 µm
Trichomes (“hairs”)
Crypt
Stomata recessed
Lower epidermal tissue
Figure Some xerophytic adaptations
Ocotillo leaves after a heavy rain
Ocotillo after heavy rain
Old man cactus

23. Loading of sucrose into phloem proton pump -- Cotransport of Sucrose
High H+ concentration
Cotransporter
Mesophyll cell
Proton pump
Cell walls (apoplast)
Companion (transfer) cell
Sieve-tube element H+ S
Plasma membrane
Plasmodesmata
Key
ATP
Apoplast
Sucrose H+ H+
Bundle- sheath cell
Phloem parenchyma cell S
Symplast
Low H+ concentration
Figure Loading of sucrose into phloem
Mesophyll cell

24. Loading of sucrose into phloem: Cotransport
High H+ concentration
Cotransporter
Proton pump H+ S
Figure 36.19b Loading of sucrose into phloem
ATP
Sucrose H+ H+ S
Low H+ concentration

25. Bulk flow by positive pressure. Pressure Flow in a sieve tube
Source cell (leaf)
Vessel (xylem)
Sieve tube (phloem) 1
Loading of sugar
H2O 1
Sucrose
H2O 2 2
Uptake of water
Bulk flow by positive pressure
Bulk flow by negative pressure 3
Unloading of sugar
Figure Bulk flow by positive pressure (pressure flow) in a sieve tube
Sink cell (storage root) 4
Water recycled 4 3
Sucrose
H2O

26. Does phloem sap contain more sugar near sources than sinks?
EXPERIMENT
25 µm
Sieve- tube element
Figure Does phloem sap contain more sugar near sources than sinks?
Sap droplet
Sap droplet
Stylet
Aphid feeding
Stylet in sieve-tube element
Separated stylet exuding sap

27. Question: Do alterations in symplastic communication affect plant development?
EXPERIMENT Results
Base of cotyledon
Root tip
Figure Do alterations in symplastic communication affect plant development?
50 µm
50 µm
Wild-type embryo
Mutant embryo

28. Wild-type seedling root tip Mutant seedling root tip
Question: Do alterations in symplastic communication affect plant development?
Experiment RESULTS
Figure Do alterations in symplastic communication affect plant development?
50 µm
50 µm
Wild-type seedling root tip
Mutant seedling root tip

29. Resource Acquisition and Transport
H2O
CO2 O2 O2
CO2
Minerals
H2O

30. Explain: Root Hairs Short Distance Transport of Water to Stele: Xylem …

31. You should now be able to:
Describe how proton pumps function in transport of materials across membranes.
Define the following terms: osmosis, water potential, flaccid, turgor pressure, turgid.
Explain how aquaporins affect the rate of water transport across membranes.
Describe three routes available for short-distance transport in plants.

32. Relate structure to function in sieve-tube cells, vessel cells, and tracheid cells.
Explain how the endodermis functions as a selective barrier between the root cortex and vascular cylinder.
Define and explain guttation.
Explain this statement: “The ascent of xylem sap is ultimately solar powered.”

33. Describe the role of stomata and discuss factors that might affect their density and behavior.
Trace the path of phloem sap from sugar source to sugar sink; describe sugar loading and unloading.